pytorch

3ef4d697 - [c10d] default backend need to check for nccl availability (#102470)

[c10d] default backend need to check for nccl availability (#102470) As titled, we can only initialize nccl backend when NCCL is available Pull Request resolved: https://github.com/pytorch/pytorch/pull/102470 Approved by: https://github.com/Skylion007, https://github.com/XilunWu